When a large molded article is injection molded, an excess part referred to as a gate is attached to the molded article. This gate is cut off with a cutter. When the gate is cut out, the molded resin article must be held down (clamped), which requires a workpiece clamp device. An example of a workpiece clamp device used in the cutting of the gate is disclosed in Japanese Patent Laid-Open Publication No. 7-276362. A workpiece clamp device used in the cutting of the gate is described hereinbelow with reference to FIG. 9 hereof.
As shown in FIG. 9, a cradle 101 of a workpiece clamp device 100 is provided with a pair of supporting plates 102, 102. A resin bumper 103 is then placed on the supporting plates 102, 102, and the resin bumper 103 is clamped by being pressed on by a pair of rods 104, 104 from above. Next, a robot arm 106 provided with a cutter 105 is brought near the resin bumper 103, and a burr 107 and gate 108, which are excess parts, are cut off by the cutter 105.
When cutting is performed with the cutter 105, the resin bumper 103 must be firmly pressed down by the rods 104, 104 so that the resin bumper 103 does not move. However, pressure marks form in the resin bumper 103 because resins are generally softer than metals. These pressure marks reduce the marketability of the resin bumper 103.
In view of this, demand has arisen for a workpiece clamp device that does not cause pressure marks.